As semiconductor devices become more integrated, and consequently the metal wiring pitches decrease, such problems as propagation delay, crosstalk noise, and power dissipation are causing concern.
To solve these problems, reducing the RC delay can initially be considered. For this purpose, resistance of the metal wiring material and conductance between each metal wire are reduced. In general, use of copper (Cu) which has good electric conductivity as a metal wiring material and a highly insulating material between the metal wires are known to be good for the purpose.
Most currently used insulating are SiO2 based materials, having a dielectric constant of 4.0. Recently, materials having a dielectric constant of 3.0 have become commercially available. Efforts are being made to reduce the constant to below 2.2 or 2.0 in the long term.
As conventional ways of reducing the dielectric constant to or below 2.5, there are a method of introducing a pore generating material into a low-dielectric matrix resin, curing it, and removing the material to obtain a porous dielectric insulating film, a method of hydrolyzing a silane compound in the presence of a base catalyst and polymerizing it to obtain a porous film, and so forth. Although low-dielectric insulating films obtained by these methods have a dielectric constant of 2.5 or less, mechanical strength decreases significantly and electric properties worsen because of the presence of pores. Thus, improvement of physical properties is required for semiconductors.
Besides having good dielectric and mechanical properties, a coating composition for a dielectric insulating film used in a semiconductor device should have particulate or metallic impurities below a given level. If particles or metal ions are present in the dielectric insulating film composition, productivity may decrease.
Also, if metals such as Na, K, Ca, Fe, Cu, Ni, Mg, and Zn or their ions are present in the dielectric insulating film composition, electric properties of the resultant dielectric insulating film may be poor. Especially, such metal ions as Na+ and K+ should be controlled to below a given level, because they diffuse fast and may cause a fatal effect on the performance of the gate device.